Chapter 8. Lego Mindstorm

Quoting the
Lego Mindstorm with Linux Mini-HOWTO
by Luis Villa:" In
case you don't know, the Lego Mindstorms Kit is a robotics kit from
The Lego Group that retails for about 200 US dollars. For that, you
get a lot of Lego pieces, a large brick containing a CPU, an LCD, and
some connectors (known as the RCX), a couple of motors, and some light
and touch sensors that allow you to interact with the outside world.
..."

"All communication to the RCX is done via the IR tower, which is
connected to the machine via a serial port. As a result, if you have
no serial port connection, you will be unable to use the RCX unless
you can buy an adapter. Furthermore, under certain circumstances,
there may be problems with IRQs or serial port conflicts. This is
particularly likely if your modem uses /dev/ttyS0."